Principles of the Use of Aged Sorption Studies in EU Regulatory Exposure Assessments

Regulatory exposure assessments for pesticides assume in the first instance that pesticide sorption is constant. Equilibrium sorption coefficients are used to predict environmental concentrations in groundwater. In Europe, the calculations can be refined considering an increase in sorption over time Caged sorption'). The U.K. Chemicals Regulation Directorate (CRD) commissioned research to underpin the development of a regulatory guidance document on aged sorption. The draft guidance proposes how to measure aged sorption of parent compounds in laboratory studies, outlines procedures to fit kinetic models to the experimental data and suggests criteria to test the goodness of fit and acceptability of the parameters. Options for use of the parameters in EU regulatory groundwater exposure assessments are highlighted. A description of the principles of the draft guidance is given in this chapter.